Influence of welding parameters and tool geometry on the morphology and mechanical performance of ABS friction stir spot welds

In the present paper, a tool with a flat pin was designed and utilized to friction stir spot weld acrylonitrile butadiene styrene sheets. Influences of welding parameters and pin geometries on joint morphology and mechanical performance were investigated. Results showed that rotational speed during plunging and stirring phase exerted a significant influence on the joint surface appearance and cross-sectional morphology while plunge rate and dwell time showed a slight effect. Secondary extrusion ring, rough weld surface, groove defects, and pores were observed under excessive stirring rotational speed. Spot weld diameter enlarged with the increase of the total tool rotation number in the plunging and stirring phase. Joint lap-shear tensile load varied significantly with the variation of the keyhole orientation. The comparison of the joints produced by different pin geometries showed that flat pin was optimal to fabricate joints with larger bonded region and lap-shear tensile load. With the increase of rotational speed or the decrease of plunge rate, joint shear strength reduced. The proper extension of dwell time under moderate rotational speed exerted a slight influence on the joint shear strength but showed a positive effect on the joint fracture load.